1. Field of the Invention
The present invention relates to a mounting structure of a rotary shaft of rotary electric machinery such as a fan motor.
2. Description of the Related Art
A rotary shaft of rotary electric machinery such as a fan motor is generally supported by a rolling bearing such as a ball bearing having a plurality of rolling elements disposed between an inner ring and an outer ring. With a rear end portion of the rotary shaft, a coming off preventing ring member as a rear side stopper rotating with the rotary shaft is fitted. Such a fan motor having the rear side stopper or the ring member is shown in FIG. 2 in U. S. Pat. No. 5,879,141. When a rotor fixed to the rotary shaft is rotating, the rotary shaft vibrates in an axial direction of the rotary shaft in the inner ring of the rolling bearing. In order to cope with such vibration, a structure in which a coil spring is disposed between the rear side stopper or the ring member and the inner ring of the rolling bearing is employed in the fan motor, for example. There is also proposed a structure in which an annular spring member or the like having a spring property is disposed between a front side stopper and the inner ring of the rolling bearing, the front side stopper being fitted with a front end portion of the rotary shaft for preventing the rotary shaft from moving to a rear side in the axial direction of the rotary shaft further than necessary.
In the conventional structure, the two members, i.e., the ring member and the spring member are used to cope with vibration of the rotary shaft in the axial direction. However, use of the two members not only increases the number of man-hours and/or manufacturing steps necessary to assemble the rotary electric machinery but also increases a price of the rotary electric machinery.
It is an object of the present invention to provide a mounting structure of a rotary shaft of rotary electric machinery in which it is possible to cope with vibration of a rotary shaft in an axial direction with a low parts count.
It is another object of the invention to provide a fan motor less expensive than a conventional fan motor.
It is yet another object of the invention to provide a fan motor that requires a lower parts count than the conventional fan motor.
The present invention improves the mounting structure of the rotary shaft of the rotary electric machinery such as the fan motor. The rotary shaft is rotatably supported by a bearing structure. The bearing structure includes one or more rolling bearings each having a plurality of rolling elements disposed between an inner ring and an outer ring for rotatably supporting the rotary shaft fitted with or inserted into an inner side of the inner ring. In general, the bearing structure is formed of two rolling bearings. The bearing structure is held by a bearing holder. A front side stopper is mounted to a front end portion of the rotary shaft projecting toward a front side (one side in the axial direction or a direction opposite to a direction in which the rotary shaft is inserted into the bearing structure) in an axial direction of the rotary shaft from the bearing structure. The front side stopper prevents the rotary shaft from moving toward a rear side (the other side in the axial direction or a direction in which the rotary shaft is inserted into the bearing structure) in the axial direction of the rotary shaft further than necessary. The front side stopper may be formed of a portion of a cup member to which a rotor is fixed in a case of the fan motor. A rear side stopper is mounted to a rear end portion of the rotary shaft projecting toward the rear side in the axial direction of the rotary shaft from the bearing structure. The rear side stopper prevents the rotary shaft from moving toward the front side in the axial direction of the rotary shaft further than necessary. A fitting groove into which a portion of the rear side stopper is fitted is formed at the rear end portion of the rotary shaft. The rear side stopper has a fitting portion to be fitted into the fitting groove and a contact portion in contact with the inner ring of the rolling bearing forming the bearing structure and the rear side stopper has a structure in which the rear side stopper generates spring force for restoring an original shape thereof when the rear side stopper is compressed in the axial direction of the rotary shaft (when forces for pinching the structure from opposite sides in the axial direction are applied). The rear side stopper is disposed in a compressed state between the fitting groove (specifically, a wall face surrounding the fitting groove) and the inner ring of the rolling bearing.
Spring force of the rear side stopper acts to suppress vibration in the axial direction of the rotating rotary shaft. In the invention, disposing of the rear side stopper in a predetermined position at the rear end portion of the rotary shaft is all that is needed. Therefore, it is possible to suppress the vibration of the rotary shaft in the axial direction with a low parts count. As a result, the number of man-hours and steps necessary to assemble the rotary electric machinery can be decreased and a price of the rotary electric machinery can be reduced.
The rear side stopper may have any structure if the structure can generate the above spring force. For example, the rear side stopper includes an annular main body fitted with the rear end portion of the rotary shaft, one or more projecting chips formed integrally with an inner peripheral portion of the annular main body and forming the fitting portion fitted with the fitting groove, and a plurality of leaf spring chips formed integrally with the inner peripheral portion of the annular main body, standing toward the front side from the annular main body, and each having at a tip end portion thereof the contact portion. The rear side stopper with such a structure can be produced easily and at low cost by applying machining to a plate made of metal. The rear side stopper may have a structure in which the plurality of projecting chips (preferably, three) are disposed at substantially equal intervals in a peripheral direction of the annular main body, the plurality of leaf spring chips (preferably, three) are disposed at substantially equal intervals in the peripheral direction of the annular main body, and the plurality of projecting chips and the plurality of leaf spring chips are disposed alternately in the peripheral direction. With such a structure, the rear side stopper can be produced by one press working. It is possible to position the rear side stopper in a stable state with respect to the fitting groove at the rear end portion of the rotary shaft and to ensure stable spring force. It is preferable that a cut portion extending in a diameter direction of the rotary shaft and forming a pair of butt portions at a portion of the annular main body is formed at a portion of the main body. If such a cut portion is formed, it is possible to relatively easily fit the plurality of projecting chips of the rear side stopper with the fitting groove of the rotary shaft.
The rear side stopper may be formed of a coil spring. In this case, the fitting groove formed at the rear end portion of the rotary shaft is formed of an annular groove completely surrounding a part of an outer periphery of the rear end portion of the rotary shaft. A portion forming a bottom face of the annular groove of the rotary shaft is formed of a cylindrical column portion positioned on the rear side and a truncated cone portion formed continuously with the cylindrical column portion and positioned forward of the cylindrical column portion. An outline or profile of the coil spring fitted into the fitting groove has a shape of a truncated cone in which a diameter of a portion positioned on an outside of the cylindrical column portion and forming the fitting portion is smaller than a diameter of a portion forming the contact portion in contact with the inner ring. In other words, the coil spring has a shape whose diameter gradually increases from one end (rear side) toward the other end (front side). If the coil spring in such a shape is used, mounting of the coil spring to the rear end portion of the rotary shaft is facilitated and the coil spring can be positioned accurately or securely.
A fan motor to which the invention is applied has the following structure. The fan motor comprises a rotary shaft, a bearing structure including two rolling bearings each having a plurality of rolling elements disposed between an inner ring and an outer ring for rotatably supporting the rotary shaft fitted with or inserted into an inner side of the inner ring, a bearing holder for holding the two rolling bearings, a motor support mounted with the bearing holder, a stator core fixed to the motor support and having a plurality of stator-side magnetic poles, a plurality of exciting windings mounted to the stator core, a cup member having a base wall portion fixed to a front end portion positioned on a front side in an axial direction of the rotary shaft and a cylindrical peripheral wall portion standing toward a rear side in the axial direction of the rotary shaft from an outer peripheral portion of the base wall portion, an impeller including a permanent magnet unit having a plurality of rotor-side magnetic poles made of permanent magnet and fixed to an inner peripheral face of the peripheral wall portion such that the magnetic poles are arranged in a peripheral direction of the peripheral wall portion and a plurality of blades disposed on an outer periphery of the peripheral wall portion of the cup member for exhaling or discharging toward the front side or the rear side, a front side stopper mounted to a front end portion of the rotary shaft projecting toward the front side in the axial direction of the rotary shaft from the bearing structure for preventing the rotary shaft from moving toward the rear side in the axial direction of the rotary shaft further than necessary, and a rear side stopper mounted to a rear end portion of the rotary shaft projecting toward the rear side in the axial direction of the rotary shaft from the bearing structure for preventing the rotary shaft from moving toward the front side further than necessary. A fitting groove into which a portion of the rear side stopper is fitted is formed at the rear end portion of the rotary shaft. The rear side stopper has a fitting portion to be fitted into the fitting groove and a contact portion in contact with the inner ring of the rolling bearing positioned on the rear side and the rear side stopper has a structure in which the rear side stopper generates spring force for restoring an original shape thereof when the rear side stopper is compressed in a direction parallel to the axial direction of the rotary shaft. The rear side stopper is disposed in a compressed state between a wall face surrounding the fitting groove and the inner ring.